Compression-relief device for internal-combustion engines



1,439,798. I H. M. CRANE. COMPRESSION RELIEF DEVICE FOR INTERNALcomausnow ENGINES.

Dec. 26, 1922.

FILED JULY 9.1921. 7

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HENRY M. CRANE, OF NEW YORK, N. Y., ASSIGNOR TO WRIGHT AERONAUTICAIZCORPORATION, A. CORPORATION OF NEW YORK.

comPRiEsslON-RELIEF DEVICE FOR INTERNAL-COMBUSTION ENGINES.

- Application filedJuly 9,

Tocll whom it may concern: Be it known that I, HENRY M. CRANE, a citizenof the United States, residing in borough of, Manhattan, city, county,and.

State of New York, have invented new and useful Improvements inCompression-Relief Devices for Internal-Combustion Engines, of'whichthe'following is a specification, reference being had to theaccompanying'drawily invention relates to a compression re lief devicefor facilitating the starting of internal. combustion engines.

A very serious and important difficulty in starting internal combustionengines is caused by the fact that-in order to turn the crank shaft of vthe engine suflicient force must be applied to compress the gas withinone of thecylinders. In a four-cycle engine, for example, during onestroke of each piston both the intake and exhaust valves are closed,sothat if an attempt is made to turn the crank shaft of the engineduring this stroke suflicient effort must be applied to compress the gascontained in the cylinder in which both valves are closed. In engines.

having four or more cylinders the compres sion is always taking place inone or another of the cylinders, so that at no time can the crank shaftbe turned without overcoming the compression resistance.

- In accordance with the present invention, movable auxiliary mechanismis provided which serves to vent each cylinder to the at mosphere onlyduring its compression stroke. The auxiliary mechanism is provided witha control by which it; may be thrown into action during starting andthrown out of action when the engine has started.

By means of the invention the compression of each cylinder may berelieved, so that the crank shaft may be turned with facility instarting the engine, while at the same time the explosive mixture drawninto the cylinders during their intake strokes is not diluted andconsequently the initial explosion may easily be obtained. This reliefof the compression may take place during a whole or a part of thecompression stroke.

While the invention may advantageously be used in connection with alltypes of internal combustion engines, including both four-cycle andtwo-cycle en 'nes, it has peculiar advantages when applied to airplane1921. Serial no. 483,637.

engines. When so used, it not only facilitates.

desired results are obtained by means of a movable auxiliary cam memberincorporated in the cam which operates the exhaust valve and arranged sothat the operator may posi-- tion it to form, on the exhaust cam, anauxiliary cam surface which serves to hold the exhaust valve openduringthe' compression stroke of each piston.

In the drawin s:

Fig. 1 is a' sectlonal elevation of the valve operating mechanism of aninternal combustion engine showing auxiliary valve members and meansfor'operating them;

Fig. 2 is a sectional plan view of one of the exhaust valve cams andassociated mechanism, taken on the line 2-2 of Fig. 1; and

Fig. 3 is a perspective view of one of the auxiliary cam members.

As shown in the d raWings,-two engine cylinders 1 and 1 are eachprovided with an intake valve 2, 2', and an exhaust valve 3, 3'. As iscustomary, the valves are provided with valve stems having at theirupper ends cam followers, 4, 5, 4, 5', and springs for retaining the camfollowers in contact with cams and holding the valves normally closed.

Above the valves is mounted a cam shaft 10 provided with a gear 11 bymeans of which it is driven from the crank shaft of the engine by meansof the usual connecting 13 which cooperate with the cam followers 5, 5to open the exhaust valves 3, 3 during the exhaust stroke of eachpiston.

The cam shaft 10 is made hollow and with in it is located mechanism foropening the exhaust valves during the compression stroke. This mechanismincludes an axially slidable rod 15 in the hollow cam shaft 10. Gne endof the rod has a running fit in a bore 16 of reduced diameter in one endof the cam shaft 10. The rod has enlarged portions 18, 18 which liewithin the portions of the hollow cam shaft 10 bearing the exhaust cams,13, 13. The enlarged portions 18, 18' have'neai; each of their endscylindrical surfaces 17, 17 which have a runningfitin the inner surfaceof the hollow shaft 10 and serve to retain the rod 15 in axial position.Between its bearing surfaces 17, the enlarged'portion 18 is providedwith a diametrically extending slot 19, and with two parallel surfaces20, each of which is inclined to the axis of the cam shaft. The enlargedportion 18' is provided with a similar slot and inclined surfaces. 7

The cam '13 is provided with a blind transverse. hole 25, which is boredin from the part of the surface of the cam which is in contact with thecam follower 5 during the compression stroke in the cylinder 1. In thehole 25 is located the auxiliary cam member 26 which, as shown in Fig.3, is in the form of a pin. Upon the outer end of the auxiliary cam.member 26 is formed a cam surface 27 which is parallel to the axis ofthe cam shaft 10. In the central part of the cam member 26 are twoopposite grooves 28, each having parallel upper and lower surfaces 29which are inclined to the axis of the cam shaftat the same angle as theinclined surfaces 20 of the enlarged portion 18 of the rod 15. For thepurposes of convenient assembly, the rod 15 may contain a transversehole 30 at the right of the inclined surfaces 20. "When the rod 15 ismoved to the left, the hole 30 becomes in alignment with the hole 25.The auxiliary cam member 26 is then inserted in the slot 19 of theenlarged portion 18 with itsinclined surfaces 29 in engagement with theinclined surfaces 20. When the auxiliary cam member has been placed inthe slot 19 its engagement with the sides of the slot and with the hole25 in the cam prevents the rod 15 from turning relatively to the .camshaft 10.

The engagement of the cam member in the slot 19 serves also to preventthe cam member from turning in the hole 25, and thus retains its camsurface 27 parallel to the axes of the cam shaft.

It is "apparent that when the .rod 15 is pushed to the left, as shown inFig. 1, the cooperating inclined surfaces 20, 29 of the enlarged portion18 and the auxiliary cam member 26 will move the auxiliary cam memberdiametrically of the cam shaft 10, so that its cam surface 27 projectsbeyond the periphery of the exhaust cam 13, forming an auxiliary camsurface upon thecam 13 which will cooperate with the cam'follower 5 toopen the exhaust valve 3 during the compression stroke in the cylinder1.

' uaaewee The parts are then in position for starting the engine.VVhen', on the other hand, the rod 17 is moved to the right, theinclined surfaces 'will draw the auxiliary cam member 26 into the bore25 in the cam 13 so that its cam surface 27 does not extend beyond theperiphery of'the cam 13'. In this, the running position, the auxiliarycam member 26 will not contact with the follower 5 so that the exhaustvalve will be opened only during the exhaust stroke in the cylinder 1.

The auxiliary cam member 26 in the cam 13"is mounted and operated in thesame way as the auxiliary cam member 26.

flontrolling means are provided for efi'ecting a longitudinal movementof the rod 15 at the will of the operator. In the form of control shownin the drawing, the rod 15.is normally held in running position by acompression spring 35 reacting between one end of the rod and of theplug 36 in the end of the hollow shaft 10. A plunger 37 slidably mountedin the casing 38 may be projected into the end of the hollow shaft 10and against one end of the rod 15. A compression spring 39 holds theplunger 37 normally out of contact with the rod and outside the hollowshaft 10. An arm 40 mounted upon the control shaft 41 extends into aslot 42 near the outer end of the-plunger 37. Suitable linkage, or othermeans, are

provided for enabling the operator to turn the shaft 11 so as to causethe arm =10 to push the plunger 37 against the rod 15.

Theuse of the device described is as follows :-lVhen the operatordesires to start the engine, he rotates the shaft .41 so as to cause theplunger 37 to push the rod 15 to the left, Fig. 1, causing thecooperating in clined surfaces to project the auxiliary cam members 26,26 beyond the peripheries of the exhaust cams 13, 13'. The crank shaftof the engine is then turned over or rotated and during this operationthe cam surfaces of the auxiliary cam members form auxiliary camsurfaces upon the exhaust cams which serve to open the exhaust valve ofeach cylinder during the compression stroke in that'cylinder.Consequently, only such force as is necessary to overcome the frictionof the moving parts need be applied in turning the crank shaft. At thesame time the proper mixture is drawn into each cylinder during itsintake stroke so that an explosion is quickly secured. As soon as theexplosions begin, the operator releases the shaft 41. whereupon thespring 39 throws the plunger 37 to-the right, Fig. 1, drawing it outlofthe hollow shaft 10 so that it does not contact with any moving part. Atthe same time the compressionspring 35 pushes the rod 15 to the right,Fig. 1, which causes the cooperating inclined surfaces to draw theauxiliary cam members 26, 26' into the exhaust cam 13, 13' so that theydo not contact with the sesses a number of important advantages.

The mechanism is extremely simple and adds little, if anything, to theWeight of the-engine. The operation of the auxiliary cam membersinvolves no movement of the cam shaft. thus making it possible to retaina bevelled gear drive for the camshaft. The mechanism causes no frictionduring the running of the engine, and only a very slight friction,namely, that between the abutting ends of the rod 15 and the plunger 37during the starting of the engine. Obviously,

the invention may be incorporated in many forms of mechanism other thanthe one here described. For example, the auxiliary cam member maybelocated on the cam shaft at a point other than within the exhaust cam.

What I claim is:

1. In an internal combustion engine, the combination with valveoperating mechanism including a cam and cam follower arranged to openthe exhaust valve during the exhaust stroke, of a movable auxiliary cammember located within the cam .shaft, controlling means arranged'toproject said auxiliary'cam member outwardly beyond the; peripheralsurface of said cam, and means for drawing said member inwardly so thatit does not project beyond the peripheral surface of the cam.

2. In an internal combustion engine, the co bination with. valveoperating mechanism including'a cam and cam follower arranged to openthe exhaust valve during the exhaust stroke, of a movable auxiliary cammember located within the cam shaft, and controlling means arranged toproject said auxiliary cam member outwardly beyond the peripheralsurface of saidcam and also to draw said member inwardly so that it doesnot project beyond the peripheral surface of the cam. a

3. In a compression relief deviceifor internal combustion engines, thecombination with a hollow cam shaft and a cam uponthe exterior of saidcam shaft, of an auxiliary cam member located in a transverse hole insaid cam and having at one of its ends an auxiliary cam surface, alongitudinally movable member within said cam shaft, adapted to'movesaid auxiliary cam member transversely of the cam shaft so as to projectits auxiliary cam surface beyond the periphery of the cam, and means formoving said longitudinally movable member in either direction.

4. In a compression relief device for internal combustion engines, thecombination with a hollow cam shaft and a cam upon the exte-- rior ofsaid shaft and containing a transverse hole, of a longitudinally movablemember within the cam shaft and containing a transverse slot, and anauxiliary cam member located in said hole and extending through saidslot, said cam member and said longi tudinally movable member havingcooperating surfaces inclined to the axis of the cam shaft and adaptedto move said cam member transversely of the cam shaft.

5. In a compression relief device for in ternal combustion engines, thecombination with a hollow cam shaft and a cam on'the exterior ofsaidshaft and containing a trans-' verse hole, of a longitudinally movablemember in the cam shaft containing a transverse slot and having at theends of said slot parallelsurfaces inclined to the axis of the shaft,and an auxiliary cam member located in said hole and engaging theinclined surfaces of said longitudinal member.

6. In a compression relief device for internal combustion engines, thecombination with a hollow cam shaft. of an auxiliary cam member mountedin said cam shaft, a longitudinally movable rod mounted within said camshaft, means whereby a longitudinal movement of said rod causes amovement of said auxiliarycam member transversely of the cam shaft, andmeans for causing a longitudinal movement of said rod in eitherdirection.

7. In a compression relief device for internal combustion engines, thecombination of a hollow cam shaft, an auxiliary cam member in said camshaft, a longitudinally movable rod mounted within said cam shaft andcontrolling the position of said auxiliary valve member, a springtending to move said rod in one direction, a slidable plunger at one endof said cam shaft, means for projecting said plunger into the end ofsaid cam shaft and into contact with said rod to move the rod againstthe opposition of said spring. and a spring tending normally to withdrawsaid plunger from the cam shaft and retain it out of contact with saidrod. 7

8. In a compression relief device for internal combustion engines, thecombination of a hollow cam shaft, an auxiliary cam member in saidcamshaft. a longitudinally mov- HENRY M. CRANE.

